Froth flotation is a commonly employed process for concentrating minerals from ores. In a flotation process, the ore is crushed and wet ground to obtain a pulp. A frothing agent, usually employed with a collecting agent, is added to the ore to assist in separating valuable minerals from the undesired or gangue portions of the ore in subsequent flotation steps. The pulp is then aerated to produce a froth at the surface thereof and the collector assists the frothing agent in separating the mineral values from the ore by causing the mineral values to adhere to the bubbles formed during this aeration step. The adherence of the mineral values is selectively accomplished so that the portion of the ore not containing mineral values does not adhere to the bubbles. The mineral-bearing froth is collected and further processed to obtain the desired minerals. That portion of the ore which is not carried over with the froth, usually identified as "flotation tailings", is usually not further processed for extraction of mineral values therefrom. The froth flotation process is applicable to ores containing metallic and non-metallic mineral values.
In flotation processes, it is desirable to recover as much mineral values as possible from the ore while effecting the recovery in a selective manner, that is, without carrying over undesirable portions of the ore in the froth.
While a large number of compounds have foam or froth producing properties, frothers widely used in commercial froth flotation operations include polyalkylene glycol compositions and alkyl ethers thereof (see, for example, U.S. Pat. Nos. 3,595,390; 2,611,485 and 2,695,101). The frothers most widely used in froth flotation operations are compounds containing a non-polar, water-repellant group and a single, polar, water-avid group such as hydroxyl (OH). Typical of this class of frothers are mixed amyl alcohols, methylisobutyl carbonol (MIBC), hexyl and heptyl alcohols, cresols, terpinol, etc. Other effective frothers used commercially are the C.sub.1 -C.sub.4 alkyl ethers of polypropylene glycol, especially the methyl ether and the polypropylene glycols of 140-2100 molecular weight and particularly those in the 400-1100 range. More recently, sulfide-containing polyalkylene oxide (U.S. Pat. No. 4,122,004) and mercaptan polyalkylene oxide (U.S. Pat. No. 4,130,477) have been found to be effective frothers as well.
Although mineral recovery improvements from a preferred frother in the treatment of an ore can be as low as only about 1 percent over other frothers, this small improvement is of great importance economically since commercial operations often handle as much as 50,000 tons of ore daily. With the high throughput rates normally encountered in commercial flotation processes, relatively small improvements in the rate of mineral recovery result in the recovery of additional tons of minerals daily. Obviously, any frother which promotes improved mineral recovery, even though small, is very desirable and can be advantageous in commercial flotation operations, especially in view of increasing energy costs.
Thus, there exists a continuing need for frothing agents which improve the selective recovery of mineral values from ores in the present flotation processes. Such improvements act not only to enhance the state of metallurgy, but can reduce the promoter consumption requirements of the mining industry as a whole.